What Materials Are Used In Norhtstars ?

Cadillacboy · #1 (**permalink**) 03-21-07, 07:18 PM

I would like to hear what you guys think of this idea. I was reading some reviews and found that :
"maybe either an all aluminum engine or an all cast iron engine. The 4.6L has a cast iron block and an aluminum head, both materials have different expansion rates paving the way for blown gaskets or cracked heads. I tip my hat to Caddy for the post-2004"

Is this right ? I knew that Northstar is all aluminum

.I am confused a bit here .However what's even more confusing to me is that those GM Engineers don't have an idea of what an engine should be made of , combined and put together ? Just because reliability problems are addressed from using different materials .
For my thoughts I would be happy if Northstars have cast iron blocks just like Vortec engine .

eldorado1 · #2 (**permalink**) 03-21-07, 07:22 PM

The 4.6L northstar is all aluminum.

The 4.9L has an iron block with aluminum heads.

The reason the 4.6L northstar blows headgaskets is because the aluminum threads in the block pull out (causing the head to be held on by fewer and fewer bolts) and/or the gasket rusts out due to improper maintenance of the cooling system.

1997BlackETC · #3 (**permalink**) 03-21-07, 07:36 PM

I just thought of a preventative maintenance idea that would prevent head gaskets from blowing on the northstars. Run a heliarc weld around the head and the block, this would keep the head from ever lifting from the block. If by some freak thing the head gasket ever did go then, just replace the engine with a rebuilt one for $3295.00. I guess they my not be too happy with the core that was turned in, but, oh well, thats life.

Cadillacboy · #4 (**permalink**) 03-21-07, 07:38 PM

Thanks for your input . I see why Northstar gets headgasket failures quite often .If it were a cast iron thouse threads wouldn't pull out

dratts · #5 (**permalink**) 03-21-07, 07:38 PM

Eldorado, I have a ton of respect for you due to the success you've had with your N* projects and the trans controller you built, but I think you have it backwards. Doesn't the 4.9 have an aluminum block and iron heads? I know that this is just the opposite of most iron/aluminum combos. I would be interested in the 4.9 if trick flow or someone made some good heads for them.

eldorado1 · #6 (**permalink**) 03-21-07, 07:44 PM

Quote:

Originally Posted by dratts

Doesn't the 4.9 have an aluminum block and iron heads?

I think you might be right

1997BlackETC · #7 (**permalink**) 03-21-07, 08:05 PM

Quote:

Originally Posted by dratts

Eldorado, I have a ton of respect for you due to the success you've had with your N* projects and the trans controller you built, but I think you have it backwards. Doesn't the 4.9 have an aluminum block and iron heads? I know that this is just the opposite of most iron/aluminum combos. I would be interested in the 4.9 if trick flow or someone made some good heads for them.

Yes, thats right, Aluminum block and Cast Iron heads. Your probabley not going to see any aftermarket makers making special head for this motor as its just not a popular hot rod motor like the Rat and Mouse chevy motors.

dkozloski · #8 (**permalink**) 03-21-07, 08:40 PM

Quote:

Originally Posted by 1997BlackETC

I just thought of a preventative maintenance idea that would prevent head gaskets from blowing on the northstars. Run a heliarc weld around the head and the block, this would keep the head from ever lifting from the block. If by some freak thing the head gasket ever did go then, just replace the engine with a rebuilt one for $3295.00. I guess they my not be too happy with the core that was turned in, but, oh well, thats life.

The first step in implementing that idea is to preheat the whole assembly to 500deg.F. That's the end of the gasket and any other sealer anywhere in the engine. That's got to be one of the most rediculous goddam schemes I've ever heard. You're not related to Al Gore are you?

dkozloski · #9 (**permalink**) 03-21-07, 09:07 PM

On a more serious note there are many examples of engines that have the heads cast with the cylinders or cylinder block and everything loads from the bottom. The Meyers and Drake Offenhauser, the Allison V1710, some Rolls-Royce Merlin versions, the Crosley Hot Shot are all enbolc with no head to crankcase joint.

**Ranger** · #10 (**permalink**) 03-21-07, 09:26 PM

Quote:

You're not related to Al Gore are you?

ewill3rd · #11 (**permalink**) 03-21-07, 09:29 PM

The N* engine is Aluminum with cast in grey iron sleeves.
The 4.9 has an aluminum block with iron cylinder inserts. Those are pretty cool in that you can replace one whole cylinder without having to rework the block. I was quite surprised at the first one I took apart.

I rarely see a N* pull head bolts that didn't overheat due to inattention or lack of maintenance FIRST.

Welding around the head is just a crazy idea, plus it wouldn't work anyway. The real pressure is nearest the cylinder where the bolts are, it could easily blow the head gasket completely loose in the center even if it was welded around the edges, not to mention the dozens of other problems that would create. I hope that was just a joke.
Actually one of the best ways to hold a head on is by using studs insted of bolts, but it costs more and it can be more complicated... but that is another topic.

The N* block and heads are all aluminum. There are lots of vehicles out there with cast blocks and aluminum heads that have little or no problem with sealing or thermal expansion variation.
Don't believe everything you read.
(except of course what I tell you

)

**Ranger** · #12 (**permalink**) 03-21-07, 10:36 PM

Quote:

Actually one of the best ways to hold a head on is by using studs insted of bolts, but it costs more and it can be more complicated... but that is another topic.

That battle has been fought before. There was a very lengthy and "heated"

discussion between someone and our old Guru about this before. Since it involved the Guru, I doubt that it can be found with a search.

CadillacSTS2003 · #13 (**permalink**) 03-21-07, 10:59 PM

dang...

eldorado1 · #14 (**permalink**) 03-21-07, 11:21 PM

Quote:

Originally Posted by Ranger

That battle has been fought before. There was a very lengthy and "heated"

discussion between someone and our old Guru about this before. Since it involved the Guru, I doubt that it can be found with a search.

The end result of which was that studs do NOTHING to help the situation specific to the northstar, because the weak link will always be the block threads.

dkozloski · #15 (**permalink**) 03-21-07, 11:34 PM

Studs are also a big production problem. Sliding head gaskets down over studs is hard to do with automatic equipment. According to Bbob, the Cadillac Northstar heads, block, head gasket and capscrews were an interlocking engineered system. A big bone of contention was always what came first, the pulled threads or corrosion. I've always suspected the metalurgical properties of the die cast block. Uneven cooling is the bugaboo of die castings and the resulting nonhomogenous grain structure causes failed threads in my scenario.